Another new feature that affects SDR video is LG's "AI Picture" setting that can be activated to have the TV analyze content on-screen and adapt its picture settings on the fly. LG explains that it is tied to a database with over 3 million samples of content and a machine learning system. This is basically next-generation picture enhancement and it is not something we can endorse. We do not agree with the sentiment that a TV's job is to enhance the picture. In our view, a TV's job is to respect the content (colors, frame rate etc) and present it in the most accurate way possible
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Switching our attention to HDR (High Dynamic Range), we measured 725 nits peak brightness on LG C9, which is actually around 100 nits lower than what we measured on last year's C8. The next milestone for OLED is hitting 1000 nits, and 100 nits difference is not too important in actual use but it is a curious development - or perhaps just variance in samples. As you can see in our measurements table, brightness starts to drop significantly at a 25% window, which means that 25% of the screen is white (while the rest is black). This is due to an embedded system called ABL (automatic brightness limiter) that regulates power consumption and driving intensity. With full-screen white (100% window), the TV manages to pump out 154 nits brightness. For HDR, LG - and LG Display - should be focused on increasing those 25-50% brightness levels. No one wants to be blinded by 500+ nits on a full-screen, so that number is less of a concern to us.
We reiterate this because it seems that many do not fully comprehend peak brightness for HDR. While 1% of a screen sounds like a small area, it is actually not very small (for example, the bright spots in the photo of the lady below are far smaller than 1%). A 1% window takes up 82944 pixels on a 4K panel. Many of the brightest elements in an HDR picture fall within such small segments. Stars, lamps, reflections in surfaces, subtitles etc. So while some LCD TVs today can theoretically hit 2000-4000 nits peak brightness, the limited luminance control of all commercial LCD panels mean that they often produce visibly lower peak brightness than OLED in actual HDR viewing, unless a much larger segment of the picture is bathed in light, for example a bright sky or a big explosion that takes up a considerable amount of screen estate. But then again, that bright sky is very unlikely to coded to 1000 or even 600 nits in the content. That is not healthy to look at and most organizations involved recommend that content creators reserve those peak brightness pops for specular highlights in the picture.
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Before we switch our attention to HDMI 2.1, we want to address the subject of brightness flashing and blocking issues. LG has released a solution for its existing TVs. We never had a chance to examine it on a 2018 LG OLED but based on what we have heard this solution seems to have been employed in 2019 LG OLED TVs as well. It works in the sense that we did not observe the issues with any of our real scene or pattern tests. But the solution bothers us. As you can see in the shot to the right, the panel now uses dithering to reproduce shades of grey
I had similarly just read a new c9 review (flatpanels are the Carlsberg of tv reviewers)